The first council to obtain a court order that prevents known gang members from associating with one another is drawing up a list of other suspects, the Guardian has been told.

The punitive terms of the initial "gang injunction" – imposed on an 18-year-old from Southwark, south London – ban him from "congregating or loitering with more than two persons in any public place" in the borough.

The new powers, which were given to police and councils at the end of January, are aimed at combating more serious and violent behaviour than the problems dealt with by asbos. They currently apply only to adults but Home Office-backed pilot projects deploying them against 14- to 17-year-olds are due to start soon.

The first person to be subject to the restrictions is a teenager who lives with his mother. He is also prohibited from entering north Peckham, an area notorious for gang violence; producing music videos that "encourage violence"; associating with "other known gang members"; or "assaulting, threatening, abusing or insulting any persons" in the borough.

He is considering appealing against the injunction. Southwark council and the police have requested that the youngster should not be identified in case he is attacked by rival gangs. Speaking at their home, his mother, who attended the county court hearing, expressed surprise at the council's decision.

"These things go back to when he was 15," she said. "I was horrified to read that he was supposed to be a notorious gang leader. I'm not sure whether we will challenge the ruling.

"It was a civil case and [the government] has cut back legal aid for civil matters. If it was a criminal case they would have to prove every allegation. But in a civil court it's just on the balance of probability." Going to a solicitor would be too expensive.

Jonathan Toy, head of community safety and enforcement at Southwark council, said: "In terms of gangs, we often find it's a very small group of people, a hard core, who affect a lot of others."

Local gangs such as the Peckham Boys, alternatively known as SN1 (Spare No One), have broken into smaller groups. "There's been a splintering of groups under all sorts of different names," Toy said.

Children as young as 12 are reported to have been caught up in gang activity and members frequently post online hip-hop videos that glorify violence.

Parents on north Peckham's worst-affected estates have complained about the danger of allowing youngsters out after dark.

"We are looking at several other [gang members] at the moment," Toy added.

"We have been working with neighbouring boroughs and they are happy to share experience. The message from our community is that they don't want to live in fear and we have to use whatever enforcement we think is appropriate."